Added check for number of active batches > 0.
Added check for number of active batches > 0.

samuelshaner/openmc,walshjon/openmc,johnnyliu27/openmc,keadyk/openmc_mg_prepush,liangjg/openmc,smharper/openmc,smharper/openmc,amandalund/openmc,mit-crpg/openmc,shikhar413/openmc,nhorelik/openmc,johnnyliu27/openmc,mit-crpg/openmc,shikhar413/openmc,mjlong/openmc,lilulu/openmc,johnnyliu27/openmc,paulromano/openmc,liangjg/openmc,shenqicang/openmc,paulromano/openmc,johnnyliu27/openmc,walshjon/openmc,liangjg/openmc,samuelshaner/openmc,nhorelik/openmc,keadyk/openmc_mg_prepush,shenqicang/openmc,mit-crpg/openmc,wbinventor/openmc,wbinventor/openmc,kellyrowland/openmc,smharper/openmc,amandalund/openmc,sxds/opemmc,walshjon/openmc,sxds/opemmc,shikhar413/openmc,wbinventor/openmc,amandalund/openmc,kellyrowland/openmc,mit-crpg/openmc,liangjg/openmc,bhermanmit/openmc,bhermanmit/openmc,lilulu/openmc,mjlong/openmc,paulromano/openmc,amandalund/openmc,paulromano/openmc,smharper/openmc,wbinventor/openmc,keadyk/openmc_mg_prepush,lilulu/openmc,bhermanmit/cdash,walshjon/openmc,samuelshaner/openmc,shikhar413/openmc,samuelshaner/openmc